On Wed, Oct 13, 2004 at 03:42:08AM +0900, aq wrote: > > > >From what I read in the mailing list, the principle of "never doing > > > this or that from inside the kernel" is repeated thousand times a day. > > > We highly appreciate the tireless education of gurus in the list to > > > the newbies like us ;-) > > > > > > For example, to read/write to file from kernelspace is always > > > undesired. And there is a solution I got from the list: to use > > > request_firmware() instead. > > > > > > But how to use request_firmware() for that trick (to read/write to > > > file)? Is that encouraged/usual solution? I looked for some examples > > > about the technique, but to no avail. > > > > request_firmware() is for a specific case of loading data that hardware > > devices need to operate. > > > > For different things you want different solutions. > > > > If you just want to load or save a configuration, you probably want to > > talk to a user-space process instead. You can use proc file, device or > > netlink socket for that. You can even start the process with > > call_usermodehelper() if there is no suitable process waiting on your > > proc-file/device/netlink-socket. > > > > The reason is, that the user-mode helper can then implement various > > policies without modifying the kernel. Eg. there might be no writable > > filesystem, but the helper can send the data to a server. If you > > insisted on writing to a file, it would be a problem. > > OK, let me show an example. I just supposed somehow I modify the ELF > loader (by patching the kernel), and I want the new loader, after > loading the executable into memory, to write the memory process to > somewhere on the disk. How can I do this, if I cannot use read/write > syscall from inside the kernel? > > I am sorry if the above example is silly. I just suppose it is the > case to clarify my confusion ;-) It is a silly example :) Don't be writing anything from the kernel to a disk file. request_firmware() is for requesting firmware to be downloaded to a device (as the documentation says...) It has nothing to do with writing a file. good luck, greg k-h -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
